An international team of researchers from Italy and the United States tested a method to protect fruit trees against fire blight. The treatment combined bentonite, a natural clay, with thyme oil. The clay helps the oil remain on flower surfaces for longer, and the mixture was tested under orchard conditions.
Fire blight is caused by the bacterium Erwinia amylovora and is a serious disease affecting fruit trees, particularly apples and pears. The bacteria can infect flowers, shoots, leaves and fruit, causing branches to blacken and dry out; severe cases can damage much of a tree.
In apple orchard trials, trees treated with bentonite and thyme oil had a 76% lower incidence of the disease. Streptomycin, the antibiotic used for comparison, produced an 81% reduction. The natural mixture therefore came close to the antibiotic in these tests, but the findings do not establish that it will perform the same way in every orchard or set of conditions.
Researchers found clay particles on flowers even nine days after application. Bentonite slows the loss of plant oil and helps its active components remain on the flower surface longer. Results nonetheless varied according to weather and application timing: in some conditions, the initial high level of protection was not achieved.
The researchers are continuing work to refine the mixture’s dosage and application method. An application for a European patent has also been filed for the method’s potential agricultural use. The findings are from orchard trials and do not, on their own, establish a universal replacement for antibiotics.